Water propulsion systems using submerged propulsion cable

ABSTRACT

A water transportation system of the kind in which a vessel is driven by a submerged moveable propulsion cable, particularly one which may assume greatly varying depth. The vessel is connected to the propulsion cable by flexible tension members, such as connecting cables, and there are winches aboard the vessel on which the connecting cables may be wound. The winches are controlled by electronic control equipment which, in addition to radio signals received from shore, is governed by tension and declivity sensors monitoring the connecting cables. Provisions of different kind are made available for changing the effective moment arm about the vessel centroid at which the members linking the vessel to the propulsion cable are connected to the hull longitudinally thereof.

United States Patent [191 Mullerheim 1 Jan. 115, 11974 1 WATER PROPULSION SYSTEMS USING SUBMERGED PROPULSION CABLE Primary ExaminerTrygve M. Blix [76] Inventor: Steven B. Mullerheim, 89 Edgecroft jif j f z fifli figq Kazenske Rd., Kensington, Calif. 94707 y e [22] Filed: Nov. 8, 1971 Appl. No.: 196,489

[56] References Cited UNITED STATES PATENTS 3,604,389 9/1971 Roberts et a1. 115/7 3,702,105 ll/l972 Feldman 114/.5 D 306,175 1l/1884 Puckett et al.... 115/7 3,541,850 ll/l970 McKechnie 73/114 244,713 7/1881 Cline 104/173 1,546,031 7/1925 Schofield 272/32 3,185,474 5/1965 Saiko 272/32 3,653,258 4/1972 King 73/114 [57] ABSTRACT A water transportation system of the kind in which a vessel is driven by a submerged moveable propulsion cable, particularly one which may assume greatly varying depth. The vessel is connected to the propulsion cable by flexible tension members, such as connecting cables, and there are winches aboard the vessel on which the connecting cables may be wound. The winches are controlled by electronic control equipment which, in addition to radio signals received from shore, is governed by tension and declivity sensors monitoring the connecting cables. Provisions of different kind are made available for changing the effective moment arm about the vessel centroid at which the members linking the vessel to the propulsion cable are connected to the hull longitudinally thereof.

9 Claims, 6 Drawing Figures PATH'HEDJAH 15 I974 sum 2 or q @NI N PATENIEUJM 15 M174 3. 785.326

SHEET 3 0F 4 ELECTRON/C CONTROL APPARATUS PATENTEDJAN 151914 3. 785326 saw u or g OIL PUMP WATER PROPULSION SYSTEMS USING SUBMERGED PROPULSION CABLE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to water transportation systems, and particularly to systems of this kind in which a vessel is driven by a submerged moveable propulsion cable.

2. Description of the Prior Art In US. Pat. No. 3,604,389 for a Water Transportation System with Shore Based Propulsion, which issued on Sept. 14, 1971 to George C. Roberts et a], there is described a cable ferry system for transportation across navigable waterways, in fact, the system is intended to be capable of crossing navigable waterways of up to several miles in length. As explained in the specification of the Roberts et al patent, the ferry system disclosed therein is superior to conventional ferries in terms of construction cost, operating cost, safety, carrying capacity, efficiency, schedule reliability and crossing time.

The system described in the reference patent comprises, among other components, a plurality of terminals, a free floating vessel, an underwater propulsion cable riding on underwater sheaves and receiving propulsion from a shore-based motor, and rigid struts for connecting the hull of the vessel to the propulsion cable and thereby causing the vessel to be moved between the terminals. While different designs for the struts for attaching the propulsion cable to the vessel are shown in the reference, a rigid member is used in the Roberts et al patent for this purpose in each case. Furthermore,

in each case the strut disclosed is shown attached at one fixed point on the vessel hull for a given direction of travel.

SUMMARY OF THE INVENTION It is one object of the present invention to improve on water transportation systems using a submerged propulsion cable andmore particularly improve on cable ferry systems of the general type described in the Roberts et al patent.

It is a more specific object of the present invention to provide in such water transportation systems new and improved means for linking the waterborne vessel ,to the underwater traction cable.

More specifically yet it is an object of the invention to improve on the linkage elements used between the vessel and the underwater propulsion cable, and on the means for controlling and changing the length of these elements.

It is another object of the invention to improve the means by which the linkage elements are attached to the vessel.

Briefly, according to a principal aspect of the invention the foregoing objects are attained by using, in lieu of rigid struts, one or more flexible tension elements for fastening the vessel to the propulsion cable and by controlling the length of these tension elements by winch means aboard the vessel. These elements may be cables, ropes, chains or the like. Flexible tension elements involve only tensile forces and they are far less expensive and far easier to replace than rigid members. Also, a flexible tension element is capable of providing a much smaller hydrodynamic cross section than a corresponding rigid member. By virtue of this it is capable of introducing considerably less resistance to the vessel system.

Although in waterborne cable vehicular systems it is not new per se to employ flexible tension elements in connecting a craft with an underwater propulsion cable, the fact that such elements, according to this aspect of the invention, are used in conjunction with the provision of winches aboard the vessel to control these elements,-gives rise to a number of unique and highly beneficial results, including the following:

1. Highly flexible and accurate changes in the length of the members may be effected. Such flexibility is not possible with the use of rigid members. Yet in many implementations of a system of the general kind disclosed in the Roberts et al patent, it can be expected that large variations in connecting member lengths will be required in the course of a journey across navigable waterways. It is assumed in the description of the Roberts et al patent that the propulsion cable lies 50 feet or more below the water surface in the channel portion and that during this portion of the crossing the connecting member will have a minimal declivity for mechanical efficiency. This requires that the connecting member would have to be on the order of feet long when outstretched to its full length. Conversely, when the vessel docks in the shallow water portions of the waterway, it would be desirable to minimize the length of connecting members for maximum control of vessel position. This would suggest member lengths of as little as 10 feet. From this example, it can be seen that a requirement of 10:1 changes in connecting member lengths would not be unusual.

2. The use of flexible tension elements for the connecting member permits the incorporation of a bridle type of construction. A bridle used as a connecting member is advantageous in increasing the azimuth stability of the vessel during its movement, even when connecting members are fastened to the vessel at a point close to the center of its longitudinal axis. From the standpoint of hull resistance, it would be desirable to fasten the member to the vessel at such a location, since the connecting member thereby introduces the minimum alteration of the hulls natural moment of trim. Thus, the use of a bridle arrangement for connecting the vessel to the propulsion as facilitated by the winch-controlled flexible tension members, according to the invention permits both a degree of angular stability and minimization of hull resistance effects.

3. The ability to change the length of the flexible tension elements through the use of winches permits the use of a simple fixed connection of these elements to the propulsion cable for all modes of operation. This obviates the need for complex and unreliable roller mechanisms as proposed in the Roberts et al patent for the rigid strut system disclosed therein.

4. In carrying out the invention precise adjustment of the flexible connecting tension members to suit various modes of operation can be effected advantageously by winch control apparatus using inputs such as the following:

a. Tension sensors. The tension of the flexible tension members can be measured by a variety of proven techniques which are more easily adapted to flexible tension elements than to rigid members. These include methods which measure the resonant frequency of the member over some prescribed length, methods which measure the transverse forces on the members required to produce a prescribed angular displacement, and methods that monitor winch motor current.

b. Declivity sensors. The angle made between the flexible tension member and the plane defined by the surface of the water can act as a control input. Conventional techniques are available for this purpose.

c. Pre-programmed units. A pre-programmed control signal based on some measure of vessel headway can be used as a winch control input. This signal can be related to the payout of propulsion cable from the terminal, for example. The signal takes into account the known depth variations of the underwater sheave systems over the course of the route, and the changes in tension and angle required during changes in mode.

Another improvement on the system shown in the Roberts et al patent is described herein relating to the means by which the connecting members between the propulsion cable and the vessel is fastened to the vessel. This improvement is advantageous irrespective of whether the connecting members are of rigid or flexible construction. In all designs disclosed in the Roberts et al patent the connecting members are attached to the hull at a fixed point for each direction of travel, although various means of pivoting this member are offered. According to an aspect of the present invention means are provided to change the effective moment arm about the vessel centroid at which the aforementioned members are connected to the hull along the longitudinal axis during the course of travel in either direction. In this manner an improvement in operating characteristics of the vessel is obtainable for the following reasons:

1. During the docking phase of operation, it is desirable to make the effective-moment arm of the connecting members about the vessel centroid as large as possible, to afford the maximum degree of hull stability for loading/unloading purposes.

2. During movement of the vessel, it is desirable to shorten the effective moment arm of these members about the vessel centroid to allow the vessel flexibility in assuming a natural angle of trim. In so doing the increase in hull resistance introduced by connecting member constraints or angle of trim will be kept low. Decreasing the effective moment arm of connecting members will, however, reduce the angular stability of the vessel, and therefore some amount of constraint will be necessary. At each speed of the vessel, a different moment arm will be required to give an optimum compromise between vessel drag and angular stability. A means of controlling this moment arm would therefore permit adjustment for optimum performance during the course of the journey, as speeds change and the lengths of the connecting members change.

Other objectives and advantages of the invention will appear from some preferred embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of a buoyant carrier attached, according to the invention, to an underwater cable by a pair of flexible cables which are controlled by winches. The connecting cables are shown in two positions which are designated by solid and dotted lines respectively and which correspond to different depths that the underwater cable can assume. Parts of the hull are broken away and shown in section.

FIG. 2 is a view in side elevation of a preferred arrangement according to the invention, generally employing the components of FIG. 1 with the addition of two winch-controlled cables which can vary the effective moment of the basic tension cables. The connecting cable system is shown in two positions designated by solid lines and dotted lines respectively.

FIG. 3 is an enlarged view of the pulley system used to link the independent cable systems of FIG. 2.

FIG. 4 is a diagrammatic view in perspective of a preferred arrangement embodying the principles of the invention and employing a bridle construction for each of two connecting cables.

FIG. 5 is a diagrammatic view in perspective of a hydraulic subsystem for changing the point along the longitudinal axis at which the connecting members between the vessel and the propulsion cable'are fastened to the vessel.

FIG. 6 is a diagrammatic view and circuit diagram of a winch motor control subsystem for use with the various arrangements according to the invention, comprising electronic control apparatus governed by cable tension sensor, cable declivity sensor and shoretransmitted signal inputs.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate some of the major features of a winch-controlled flexible connecting member arrangement embodying the principles of the invention. Referring first to FIG. 1, two winch systems I and 2, symmetrically displaced longitudinally of the center of the hull of vessel 10 control the lengths, tensions and declivities of two independent cables 3 and 4 which are firmly attached to the underwater propulsion cable 5 by pvioting at points 6 and 7. Each cable 3, 4 leaves the hull 70 of the vessel 10 over pulley systems 8, 9 each of which is mounted so as to allow variation in both cable azimuth and declivity. Each cable is monitored by both a declivity sensor 11, 12 and a tension sensor 13, 14 which serve as inputs to the winch control apparatus 15. As more particularly shown in FIG. 6, the control system also receives as an input telemetered data from the shore-based propulsion motor system, not shown, via a radio link of which antenna 16 is a part. By changing the relative and absolute lengths of the two connecting cables, an infinite variety of cable tensions and declivities can be provided. In FIG. 1, two cable configurations, the significance of which will be more fully appreciated from the description given hereinafter of FIG. 2, are shown by the dotted and solid lines respectively.

The system of FIG. 1 utilizes pulleys 8, 9 which are fixed in their longitudinal location and provides no facilities whereby the moment arm of the cables about the centroid 17 of the vessel 10 may be varied. This requires that the pulleys be situated at a point fairly distant from the vessel centroid yielding some compromise between azimuth stability and bull resistance. In FIG. 2, an improved system is shown which allows the moment arm to be independently varied for each of the two connecting cables 3, 4 by means of two additional deflecting cables l8, l9 controlled by associated winches 20, 21 in connection with pulleys 62, 63 which again are mounted to permit variation in both declivity and azimuth. This allows the pulleys 8', 9 to be located near the vessel centroid, for minimum hull resistance during movement. It will be noted that, with this in mind, the pulleys 8', 9' have been placed on the opposite side of their respective winches l and 2 as compared with the relative locations of the otherwise similar pulley systems 8, 9 and associated winch systems 1, 2 in FIG. 1. Cables 18 and 19 fasten to connecting cables 3 and 4, respectively, by pulley systems 60 and 61, which, as indicated in greater detail in FIG. 3 for pulley system 61, allow deflection cables 18 and 19 to slide freely over the connecting cables. Each of the four cable systems is equipped with its own set of declivity sensors 11, 12, 22 and 23, and tension sensors 13, 14, 24 and 25. As will become clearer from the diagrammatic showing of FIG. 6 described below, all sensors serve as inputs to the winch control apparatus 15 which also receives telemetered data from the shoremotor station, as in FIG. 1.

In normal operation, the system of FIG. 2 will have several modes of operation, each of which will require different cable configurations. Two are shown in FIG. 2 by the broken lines and solid lines respectively. The solid line indicates the assumed running configuration for a deep water channel with movement from left to right. In this case, the forward connecting cable 4 assumes a minimum declivity and the deflection cable 19 is slack, thereby permitting maximum forward thrust and minimum interference with the vessels natural mo- I ment of trim. The rear deflection cable 18 is slightly taut, thereby providing a degree of azimuth stability which can be varied by changing the relative lengths of cables 3 and 18. The dotted line cable configuration represents that of clocking in shallow water, wherein both deflection cables are held firmly taut for maximum stationarity of the vessel during loading and unloading.

FIG. 4 shows an alternative cable system to that of FIG. 1 in which two cable bridles 26 and 27 are substituted for the two single cables 3 and 4 of FIG. 1. The

two bridles are controlled by two associated winches 28, 29 each however, provided with two separate drums 30, 31 and 32, 33 one for each of the two b'ridle leads, 26a, 26b and 27a, 27b, respectively. Each bridle lead is separately conducted to a pulley system 34, 35 36, 37 which again is mounted so as to allow the lead to assume various declivities and azimuths. Through the use of bridles, an extra degree of vessel stability is obtained in aximuth. For this reason the pulley systems can be located closer to the centroid of the vessel than in FIG. 1, thereby introducing less constraints on the natural angle of trim, and correspondingly, introducing less hull resistance. In other respects, the vessel of FIG. 4 is identical to that of FIG. 1 although it will be noted that in FIG. 4 the positions of the pulleys relative to their associated winches have been reversed as in FIG.

FIG. 5 shows a hydraulic subsystem that may be used for changing the point along the longitudinal axis of the hull, at which the connecting members apply their forces. TWo hydraulic pistons 40, 41 move associated sliding tables 42, 43 which ride on a set of tracks 44, 45. In FIG. 5 it has been assumed that the two sliding tables carry pulley systems 34, 35 and 36, 37, respectively, of the bridle arrangement shown in FIG. 4 and that they are used for changing the distance longitudinally of the hull axis, between these two sets of pulley systems. However, the arrangement of FIG. 5 may also be used where single cables rather than bridle-type cables are employed. In this case the two sliding tables could carry pulleysystems such as 8', 9, FIG. 2, for example. Alternatively, the two sliding tables can also be supplied with pivoting assemblies if strut means are used for connecting to the propulsion cable. In the embodiment illustrated in FIG. 5, the hydraulic pistons 40, 41 receive their thrust through a pump 46 from an oil reservoir 47, with solenoid-actuated valves 48, 49 controlled in a manner not particularly shown in the drawings, by a winch control apparatus similar to that designated by reference numeral 15 in FIG. 6.

In FIG. 6 the winch control system is diagrammatically .illustrated in greater detail, with inputs and outputs of the electronic control apparatus 15 specifically shown for only one of the several winch systems. FIGS. 1 or 2, that will be used. The control of winch 1', FIG. 2, has been singled out by way of example. Antenna 16 which forms a part of the radio link to the shore propulsion system, not shown, provides pre-programmed instructions on desired cable declivities, tensions, and lengths, as determined by vessel headway, vessel mode, and stored data on the contour of the underwater sheave assembly. Signals provided by tension sensor 13 and declivity sensor 11' serve to monitor the condition of cable 3 and provide corrective feedback. The other winch systems are controlled by control apparatus 15 in a similar manner, as schematically indicated in FIG. 6.

By way of summary, it will be appreciated from the foregoing description that the use of winches aboard the vessel to control, in accordance with the principles of this invention, the length, tension and declivities of flexible tension elements connecting the craft with an underwater propulsion cable gives rise to considerable advantages such as those enumerated above. Equally beneficial is the use of power means to shift the effective moment arm of connecting members about the centroid of the vessel, and this holds for both flexible tension elements and rigid means of connection. It should be noted, however, that all embodiments described herein are purely illustrative of the varying aspects of the invention and are not intended to be in any sense limiting.

I claim:

1. An arrangement for connecting a vessel of a water transportation system to a moveable propulsion cable which is submerged at varying depths, said arrangement comprising winch means aboard said vessel and two flexible tension means fixedly attached to said cable at longitudinally spaced points thereof and adapted to be wound on said winch means, said two flexible tension means leaving said vessel at locations fore and aft, respectively, of the centroid of said vessel, which in projection, are disposed longitudinally inwardly of the points of attachment of the corresponding tension means to said propulsion cable, and at angles independently adjustable by the corresponding winch means.

2. The arrangement of claim 1, further comprising means for separately monitoring the declivities and/or tensions of the fore and aft flexible tension means, and control apparatus governed by said monitoring means for separately controlling the winch means for said fore and aft tension means so as to vary the length, declivity and for tension of the corresponding tension means in accordance with the depth of submersion and direction of movement of said propulsion cable.

3. The arrangement as claimed in claim I wherein said locations at which the flexible tension members means leave the vessel are disposed along the longitudinal center plane thereof.

4. The arrangement as claimed in claim 1 wherein said flexible tension means comprise connecting cables which are bridle-shaped at their upper ends, the two arms of said bridle leaving said vessel at locations spaced transversely of said vessel.

5. The arrangement as claimed in claim 1 wherein said arrangement comprises power-operated means aboard said vessel for changing the effective moment arm of said flexible tension means about the centroid of said vessel fore and aft, respectively, of said centroid.

6. THe arrangement as claimed in claim 5 wherein said power-operated means include deflecting cables engaging the corresponding flexible tension members at an intermediate point thereof, and additional winch means respectively associated with said deflecting cables, said deflecting cables being adapted to be wound on their associated winch means, thereby to change the deflection of said flexible tension members and hence the effective point of their connection to said vessel longitudinally thereof.

7. The arrangement as claimed in claim 5 wherein said flexible tension members leave said vessel ovcr fore and aft pulley means mounted for movement longitudinally of said vessel, and wherein said power operated means are arranged to alter the longitudinal spacing of said fore and aft pulley means with respect to each other.

8. Tl-le arrangement as claimed in claim 7 -wherein said fore and aft pulley means are mounted on carriers moveable on tracks extending longitudinally of the vessel, and wherein said power-operated means include hydraulically actuated pistons for altering the spacing of said carriers longitudinally of said vessel.

9. An arrangement for connecting a vessel of a water transportation system to a submerged moveable propulsion cable, comprising connecting members between said vessel and said cable, and a power operated means aboard said vessel for changing the effective moment arm of said members about the centroid of said vessel longitudinally thereof. 

1. An arrangement for connecting a vessel of a water transportation system to a moveable propulsion cable which is submerged at varying depths, said arrangement comprising winch means aboard said vessel and two flexible tension means fixedly attached to said cable at longitudinally spaced points thereof and adapted to be wound on said winch means, said two flexible tension means leaving said vessel at locations fore and aft, respectively, of the centroid of said vessel, which in projection, are disposed longitudinally inwardly of the points of attachment of the corresponding tension means to said propulsion cable, and at angles independently adjustable by the corresponding winch means.
 2. The arrangement of claim 1, further comprising means for separately monitoring the declivities and/or tensions of the fore and aft flexible tension means, and control apparatus governed by said monitoring means for separately controlling the winch means for said fore and aft tension means so as to vary the length, declivity and for tension of the corresponding tension means in accordance with the depth of submersion and direction of movement of said propulsion cable.
 3. The arrangement as claimed in claim 1 wherein said locations at which the flexible tension means leave the vessel are disposed along the longitudinal center plane thereof.
 4. The arrangement as claimed in claim 1 wherein said flexible tension means comprise connecting cables which are bridle-shaped at their upper ends, the two arms of said bridle leaving said vessel at locations spaced transversely of said vessel.
 5. The arrangement as claimed in claim 1 wherein said arrangement comprises power-operated means aboard said vessel for changing the effective moment arm of said flexible tension means about the centroid of said vessel fore and aft, respectively, of said centroid.
 6. The arrangement as claimed in claim 5 wherein said power-operated means include deflecting cables engaging the corresponding flexible tension members at an intermediate point thereof, and additional winch means respectively associated with said deflecting cables, said deflecting cables being adapted to be wound on their associated winch means, thereby to change the deflection of said flexible tension members and hence the effective point of their connection to said vessel longitudinally thereof.
 7. The arrangement as claimed in claim 5 wherein said flexible tension members leave said vessel over fore and aft pulley means mounted for movement longitudinally of said vessel, and wherein said power operated means are arranged to alter the longitudinal spacing of said fore and aft pulley means with respect to each other.
 8. The arrangement as claimed in claim 7 wherein said fore and aft pulley means are mounted on carriers moveable on tracks extending longitudinally of the vessel, and wherein said power-operated means include hydraulically actuated pistons for altering the spacing of said carriers longitudinally of said vessel.
 9. An arrangement for connecting a vessel of a water transportation system to a submerged moveable propulsion cable, comprising connecting members between said vessel and said cable, and a power operated means aboard said vessel for changing the efFective moment arm of said members about the centroid of said vessel longitudinally thereof. 